The human microbiome has emerged as a key modulator of host immunity, influencing responses to cancer immunotherapy across various malignancies. This review explores the dynamic interplay between the gut microbiota and immune checkpoint blockade (ICB), discussing mechanisms by which microbial diversity and composition modulate antitumor immunity. We examine clinical studies linking specific bacterial species with treatment efficacy, the impact of antibiotics and probiotics, and the emerging role of fecal microbiota transplantation (FMT) in overcoming resistance to immunotherapy. Challenges in standardizing microbiome-based interventions and the need for personalized microbial strategies are addressed. With a focus on melanoma, lung, and gastrointestinal cancers, this article integrates current evidence and future directions to highlight the translational potential of the microbiome-immunotherapy axis in precision oncology.
Sayyed et al. (2026) studied this question.